FIG. 1 shows one example of conceivable configuration of VOD (Video On Demand) system using the ATM (Asynchronous Transfer Mode) network at the backbone side and the IEEE (The Institute of Electrical and Electronic Engineers, Inc.) 1394 serial bus (IEEE 1394 Standards Draft 8.0v2) at the front end side.
An ATM terminal 1 is a server for storing video data, etc., and is connected to an ATM network 2 through UNI (User-Network Interface) to make an offer of video data to 1394 terminals 4-1 to 4-7 (hereinafter referred to as 1394 terminals 4 as occasion may demand when there is no necessity to individually discriminate between 1394 terminals 4-1 to 4-7). An ATM/1394 repeater 3 is connected to the ATM network 2 through UNI and serves to receive video data transmitted from the ATM terminal 1 via the ATM network 2 to make an offer thereof to the 1394 terminals 4 through the IEEE 1394 serial bus. The 1394 terminals 4 receive video data offered through the IEEE 1394 serial bus from the ATM/1394 repeater 3 to display them on respective display units such as CRT or LCD, etc.
In this VOD system, when the ATM terminal 1 carries out communication between the ATM terminal 1 and any 1394 terminal 4, protocol peculiar to ATM must be entirely terminated at the ATM/1394 repeater 3.
In the case where IP over ATM (hereinafter abbreviated as IP/ATM) is used as the standard protocol when, e.g., the ATM terminal 1 carries out transmission/reception of IP (Internet Protocol) packet between the ATM terminal 1 and the 1394 terminal 4, protocol stacks of the U (User) plane and the C (Control) plane of end to end are caused to respectively undergo layout as shown in FIGS. 2 and 3.
Namely, as shown in FIG. 2, the protocol stack of the U plane of the ATM network 2 consists of PHY (physical) layer and ATM layer. Accordingly, the protocol stack of the U plane of the ATM terminal 1 includes PHY layer and ATM layer in correspondence with the ATM network 2, and includes IP/ATM layer and IP layer for carrying out transmission/reception of IP packet. Further, between the ATM layer and the IP/ATM layer, the protocol stack of the U plane of the ATM terminal 1 includes AAL (ATM Adaptation Layer) 5 for carrying out matching/adjustment between data unit (user information from 1 byte up to 64 k bytes) of the high order (upper) application (IP/ATM layer) and user information of 48 bytes handled by cell in a unified manner.
In the protocol stack of the U plane of the ATM/1394 repeater 3, the ATM network 2 side is caused to be of structure similar to the ATM terminal 1. Namely, this protocol stack consists of PHY layer, ATM layer, AAL5 layer, IP/ATM layer and IP layer. On the other hand, the 1394 terminal 4 side is caused to be of structure similar to the protocol stack of the 1394 terminal 4 and consists of 1394 PHY layer, 1394 LINK layer and IP layer. There is no layer corresponding to the IP/ATM layer of the ATM network 2 side (Therefore, labeled null in FIG. 2) (It is to be noted that it is conceivable to place (allocate) protocol like IP/1394). The protocol stack of the U plane of the 1394 terminal 4 consists of 1394 PHY layer, 1394 LINK layer and IP layer.
Moreover, as shown in FIG. 3, the protocol stack of the C plane of the ATM terminal 1 consists of PHY layer, ATM layer, AAL5 layer, SSCF (Service Specific Coordination Function) (ITU (International Telecommunication Union)-TQ.2130)+SSCOP (Service Specific Connection Oriented Prtocol) (ITU-TQ.2110) layer, and Q.2931 (ITU-TQ.2931) layer. The protocol stack of the C plane of the ATM network 2 is caused to be of structure similar to the case of the ATM terminal 1.
In the protocol stack of the C plane of the ATM/1394 repeater 3, the ATM network 2 side is caused to be of structure similar to the case of the ATM terminal 1 and the ATM network 2. On the other hand, the 1394 terminal 4 side is caused to be of structure similar to the protocol stack of the 1394 terminal 4, and consists of 1394 PHY layer, 1394 LINK layer and Original Signaling Protocol layer. The protocol stack of the C plane of the 1394 terminal 4 consists of 1394 PHY layer, 1394 LINK layer and Original Signaling Protocol layer.
Since the concept of VPC (Virtual Pass Connection)/VCC (Virtual Channel Connection) does not exist between the ATM/1394 repeater 3 and the 1394 terminal 4 as shown in FIG. 2, it is conceivable to carry out handling of packet of the U plane by IP header. In that case, for the ATM/1394 repeater 3, routing function by IP is required.
Moreover, since the signaling protocol (Q.2931 layer and SSCF+SSCOP layer) used in UNI of the ATM network 2 cannot be applied between the ATM/1394 repeater 3 and the 1394 terminal 4 as shown in FIG. 3, it is necessary to peculiarly design original signaling protocol corresponding thereto to use such protocol.
However, in the ATM/1394 repeater 3, in the case where handling of packet of the U plane is carried out by using the routing function by IP, it is necessary to copy the entirety of IP packet including data to read therefrom information necessary for routing, resulting in the problem that burden (load) applied to the ATM/1394 repeater 3 is great.
In addition, there occurs the necessity of developing the original signaling protocol used between the ATM/1394 repeater 3 and the 1394 terminal 4 from the first stage. To realize this, great amount of investment is required, resulting in the problem that such approach was not realistic.